Yahya related to me from Malik from al-Ala ibn Abd ar-Rahman ibn Yaqub that Abu Said, the mawla of Amir ibn Kuraz told him that the Messenger of Allah ﷺ called toUbayy ibn Kab while he was praying. When Ubayy had finished his prayer he joined the Messenger of Allah ﷺ and the Messenger of Allah put his hand upon his hand, and he was intending to leave by the door of the mosque, so the Messenger of Allah ﷺ said, "I hope that you will not leave the mosque until you know a sura whose like Allah has notsentdown in the Tawrah nor in the Injil nor in the Qur'an." Ubayysaid, "I began to slow down my pace in the hope of that. Then I said, 'Messenger of Allah, the sura you promised me!' He said, 'What do you recite when you begin the prayer?' I recited the Fatiha (Sura 1 ) until I came to the end of it, and the Messengerof Allah ﷺ said, 'It is this sura, and it is the "seven oft-repeated" and the Great Qur'an which I was given.' "  

أَخْبَرَهُ أَنَّ رَسُولَ اللَّهِ ﷺ نَادَى أُبَىَّ بْنَ كَعْبٍ وَهُوَ يُصَلِّي فَلَمَّا فَرَغَ مِنْ صَلاَتِهِ لَحِقَهُ فَوَضَعَ رَسُولُ اللَّهِ ﷺ يَدَهُ عَلَى يَدِهِ وَهُوَ يُرِيدُ أَنْ يَخْرُجَ مِنْ بَابِ الْمَسْجِدِ فَقَالَ إِنِّي لأَرْجُو أَنْ لاَ تَخْرُجَ مِنَ الْمَسْجِدِ حَتَّى تَعْلَمَ سُورَةً مَا أَنْزَلَ اللَّهُ فِي التَّوْرَاةِ وَلاَ فِي الإِنْجِيلِ وَلاَ فِي الْقُرْآنِ مِثْلَهَا قَالَ أُبَىٌّ فَجَعَلْتُ أُبْطِئُ فِي الْمَشْىِ رَجَاءَ ذَلِكَ ثُمَّ قُلْتُ يَا رَسُولَ اللَّهِ السُّورَةَ الَّتِي وَعَدْتَنِي قَالَ كَيْفَ تَقْرَأُ إِذَا افْتَتَحْتَ الصَّلاَةَ قَالَ فَقَرَأْتُ الْحَمْدُ لِلَّهِ رَبِّ الْعَالَمِينَ حَتَّى أَتَيْتُ عَلَى آخِرِهَا فَقَالَ رَسُولُ اللَّهِ ﷺ هِيَ هَذِهِ السُّورَةُ وَهِيَ السَّبْعُ الْمَثَانِي وَالْقُرْآنُ الْعَظِيمُ الَّذِي أُعْطِيتُ  

Yahya related to me from Malik from Abu Nuaym Wahb ibn Kaysan that he heard Jabir ibn Abdullah say, "Someone who prays a raka without reciting the umm al-Qur'an in it has not done the prayer except behind an imam."  

يَقُولُ مَنْ صَلَّى رَكْعَةً لَمْ يَقْرَأْ فِيهَا بِأُمِّ الْقُرْآنِ فَلَمْ يُصَلِّ إِلاَّ وَرَاءَ الإِمَامِ